A heat-sensitive recording system using a heat-sensitive recording material comprising a support having thereon a heat-sensitive recording layer is well known and widely applied to facsimiles and printers, in which a thermal head passes over the recording material in contact therewith to transfer heat energy to the heat-sensitive recording layer either directly or via a protective layer, thereby recording a colored image. In such a heat-sensitive recording system, since the thermal head is in contact with the heat-sensitive recording material and passes thereover, it becomes abraded and worn, or the constituents of the heat-sensitive recording material adhere to the surface of the thermal head, which often results in the failure of the thermal head to reproduce an accurate image or leads to the destruction of the head.
Further, as a result of the structural characteristics of the thermal head, there are limits on the high speed control of the heating and cooling of the heating element and on the density of the heating element, which have made it difficult to achieve high performance recording features such as high speed recording and high density and high quality recording.
In order to overcome these problems associated with heat-sensitive recording systems using a thermal head, the use of a laser beam as an energy source to conduct thermal recording without placing a thermal head in contact with a heat-sensitive recording material and to achieve high speed and high density recording has been disclosed, e.g., in WO 884237A, JP-A-50-23617, JP-A-54-121140, JP-A-57-11090, JP-A-58-56890, JP-A-58-94494, JP-A-58-134791, JP-A-58-145493, JP-A-59-89192, JP-A-60-205182, and JP-A-62-56195 (the term "JP-A" as used herein means an unexamined published Japanese patent application). With such a laser beam recording system, though, a considerably high laser output is required for obtaining the heat energy necessary for coloration, because a heat-sensitive recording layer, in general, hardly adsorbs light in the visible and near infrared regions. Therefore, it is very difficult to make a small-sized and inexpensive recording device containing a laser.
In this regard, many techniques have been proposed to provide efficient absorption of laser light into a heat-sensitive recording layer. A commonly applied technique is to add a substance capable of absorbing light of the same wavelength as a laser beam to the heat-sensitive recording layer. In this case, the light absorbing substance to be added must be white. Otherwise, the recording material will provide a recorded image of low quality due to low contrast. In general, many white light-absorbing substances are inorganic compounds, and most of the inorganic light absorbing substances have a low light-absorbing efficiency. No organic compound having a satisfactory light-absorbing efficiency while being free from coloration has been developed yet.